The Senate Judiciary Committee will attempt during a closed-door hearing Wednesday to get to the bottom of the alleged “unmasking” of Trump campaign and transition officials by the Obama White House — furthering a potentially explosive counter-narrative coursing beneath the various congressional probes into alleged Russian meddling in the 2016 presidential election.

Former National Security Adviser Susan E. Rice, in addition to other top officials from the Obama administration, have come under suspicion during recent months amid accusations that they inappropriately “unmasked” requests to identify Trump associates caught up in clandestine surveillance of Russian operatives prior to and during the immediate aftermath of the November election.

While Republican lawmakers have during recent months led the charge for a deeper investigation into the unmasking allegations, it was a key Democrat on the Judiciary Committee who raised the issue during a public committee hearing on Tuesday, asserting that lawmakers hope to explore it more deeply with FBI officials during a secret hearing slated for Wednesday.